Auxiliary illumination, ceiling illumination, illumination for showcases, or other types of conventional illumination have been carried out with light-emitting devices for spotlighting that illuminate a specific area with radiating light in a specific direction. Recently, white-light emitting diodes (white LEDs) have been used as light sources of light-emitting devices for spotlighting.
White-light emitting diodes, which are small, power-efficient semiconductor devices emitting bright colored light, have characteristics such as no burnout, superior initial driving characteristics, and high durability against vibration and repeated on/off switching operations.
Light-emitting devices for spotlighting are also known that control the distribution characteristics of light emitted from a light-emitting diode through an illumination lens symmetrical about the optical axis of the light-emitting diode (for example, Patent Literature 1). According to Patent Literature 1, a lens having a total-reflection surface on the emission side of the light-emitting diode is disposed such that the light from the light-emitting diode at a large angle to the optical axis is incident on the lens and then is totally reflected at the total-reflection surface to emit light with a narrowed distribution. According to Patent Literature 1, an opaque cylindrical external cover that supports the upper portion of the lens and surrounds the sides of the lens is also provided to efficiently radiate the light totally reflected at the total-reflection surface of the lens, forward from the lens.
A light-emitting device for spotlighting is also known that includes a cylindrical illumination lens or an illumination lens that is rotationally-symmetrical about the optical axis of the light-emitting diode. Such an illumination lens is disposed on the emission side of the light-emitting diode and focuses the light emitted from the light-emitting diode onto a target surface.